Step 1: Prepare the Board and Power Supply

Unscrew the output terminals.

Using the de-soldering pump, remove the one-off switch can any of the outputs that you don't wish to use. I removed the -12V LED as I do not wish to use the -12V outputs.

Solder leads onto each of the outputs, terminating each one with a washer. You may need to file the washers down a little in order to get the solder to attach properly to them.

While not necessary, in order to keep things as neat as possible I opened the power supply, disconnecting all leads that would not be used by the breakout board. De-soldering them proved to be rather difficult and so I simply cut them, making the ends safe using heat-shrink tubing.

Solder on the leads that will be use to connect to the switch.

Step 2: Printing the Case

The model was created using FreeCAD. If you wish to edit it, download "PowerSupplyV2.fcstd.txt", renaming to
"PowerSupplyV2.fcstd".

Initially I printed the case in two colours i.e. the main sections of the case in back and the numbers in glow-in-the-dark filament. The numbers however broke off and so I then printed them as three separate pads, gluing them on. Before printing these pads, I scaled them down to be 10mm wide.

Step 3: Putting It All Together

Screw the breakout board into the base.
Attached the output terminals to the top part of the case.
Push the attached washers onto the remaining threads of the corresponding terminals and bolt them down.
Thread the switch leads through the side switch hole and solder them to the rocker switch, inserting the switch afterwards.
Place the top o the case over the base and line it up with where you want it to sit on the ATX power supply. Mark where the holds should go, using a drill to drill them out.
Using the nuts and bolts, attach the box to the top of the power supply.
Plug the ATX cables into the breakout board and test.
Use cable ties to tidy-up any cabling.

(You may need to file the edges of the case a little so that the ATX connector fits properly)

You should now have a cheap but neat and functional power supply to test your projects on.